Process of repulping old or waste paper



' UNITED STATES rATE vT OFFICE.

JOHN M. BURBY, 0F WEBSTER, MKSSACHU SETTS.

raocnss or REPULPING OLD on WASTE PAPER.

No Drawing.

To all whom it may concern:

Be it known that I, JOHN M. BURBY, a citizen of the United States, residing at Webster, in the county of Worcester and State of Massachusetts, have invented a new and useful Process of Repu'lping Old or Waste Paper, of which the following is a pe ification This invention relates to a process of repulping old or waste paper and particularly to a process for making a high grade chemical pulp from old news print or other similar grades of paper.

In the manufacture of paper pulp from wood, several different processes are used. The better grades of pulp are known to the trade as chemical pulp and are made by subjecting small chips or pieces of wood to the action' of certain chemicals which dissolve the pitch and other binding materials which hold the wood fibers together, thereby freeing the fibers so that they may be readily matted or felted together, From this chemical pulp the better grades of paper are manfree from raw or undigested wood s The 'pulp from which news print and other cheap papers are made is termed mechanical wood pulp and is made by rinding the raw wood to small particles w ich' are thereafter washed and graded and then collected to form sheets of convenient size.

This pulp is much inferior to the chemical pulp inf strength and can only be used for very cheap grades of aper, as the raw wood particles change 00 or upon exposure to light. Even when so used it is commonly necessary to add a certain percentage of chemical pulp in order to produce a workable paper.

News print and other papers formed from mechanical wood ulp contain from forty-to ninety per cent. of raw or undigested ground wood and it is not possible to repulp such papers by any processheretofore nown, in such a manner as to produce high grade paper therefrom,

It is the object of my present invention to provide a process by which a high grade chemical pulp may be made from news print or other cheap papers containing a large amount of raw wood.

With this object in view my invention re- 1 lates to a certain sequence of operations by which the old paper and the raw or ground Specification of Letters Patent.

Application filed April 14, 1916. Serial No. 91,213.

ufactured and these papers are practically Patented Jan. 6, 1920.

wood contained therein may be transformed into chemical pulp.

In the carrying out of my improved process, the old paper is first. reduced to pieces of' convenient size by means of wellnown machines customarily used for this urpose.

If a particularly light-colored and high grade pulp is desired, it may be advisable to subject the paper to the action of analkaline solution, in order to remove the ink and coloring matter therefrom, this action taking place at a comparatively low temperature and never above the boiling point of water This preliminary treatment, while often desirable, is not an indispensable step in my process, as a very satisfactory pulp for many purposes can be made without the preliminary alkaline treatment.

In the further carrying out of my process the waste paperyeither untreated or treated with alkali as above described, is placed in a solution of suitable chemicals and is boiled therein fora period of time sufficient to permit these chemicals to convert theraw or ground lwood fibers into chemical pulp. I have found that a considerable range of chemicals may be used for attaining this re-- sult, and the selection of chemicals depends largely upon the grade, or kind of chemical pulp desired.

' I secure a better grade of pulp by boiling the waste paper in a solution containing bisulfite of calcium, magnesium or sodium, the pulp thus obtained corresponding to the so-called sulfite pulp of commerce and possessing strong fibers firmly matted or felted together. This pulp is very light in color andmay be used with oriwithout supplementary bleaching in the production of high grade book papers.

By boiling the old paper in a solution containing sodium sulfate, with or without the addition of caustic soda and sodium carbonate, I secure a pulp of darker color corresponding to the so-called sulfate pulp or kraft of commerce. 2

While I have attained good results by the use of the chemicals named, I do not wish to be understood as limitin my process to the use of any articular c emicals except asset forth in tl ie claims, as I have also attained good results from the use of sodium sulfi-d and also by the use of other chemical blocks or chips.

sential "feature is that the chemicals, when used at a temperature above 212 F., should be eflectiveto digest the raw wood of the news print and other-cheap papers, and to transform the same into a strong chemical pulp. v

The period of time necessary for this treatment varies with the chemicals used, and under ordinary circumstances will be from four to eight hours. The action of the chemicals is more rapid and the time is reduced if the boiling process is carried out in a suitable closed tank or di ester under pressures which may run as hig as seventy or eighty pounds or more.

After the boiling process is completed, the pulp is removed and may then be sent through a beating engine by which the fibers are torn apart and the pulp is thoroughly washed. -The -pulp is then removed for bleaching if desired and is finally collected and passed under rollers by which it is pressed into sheets convenient for shipment.

and handling.

The chemical pulp thus obtained is suitable for any of the purposes to which similar pulp made from wood chips may be applied,

the character of the pulp depending somea what upon the chemicals used as above described.

The ground wood contained in old paper is more accessible to the action of the digest ing solution than is wood in the form of The solution may therefore be of much less strength and the time required for boiling is also correspondingly less. When carrie of the solutions is merely nominal.

out in this way the cost Having thus described my invention in detail, it will be evidentthat other chan es and modifications can be made therein Ty those skilled in the art without departing from the spirit and scope thereof as set forth in the claims and I do not wish to be otherwise limited to the details herein disclosed, but what I do claim is 1. The process of converting old paper made from mechanical wood pulp into chemical wood pulp by boiling said paper in a solution containing chemicals effective to act upon the mechanical wood pulp of the old paper and to reduce said wood pulp to the nature of a chemical wood pulp.

pulp by boiling said old paper in a digester under pressure above atmospheric, said digester containing chemicals. effective to act upon the ground wood of the old paper and to reduce said 3. The process of converting old paper containing ground wood into chemical wood pulp by boiling said old paper in a solution of chemicals containing sulfur, in a form efiective to reduce the ground Wood of the old. paper to the nature of, a chemical wood pulp.

4. The process of converting old paper containing ground wood into chemical wood pulp, which consists in boiling said old paper in a bisulfite solution of suflicient strength to change the old paper into chemical wood pulp.

In testimony whereof I have: hereunto set my hand.

JOHN M. BURBY.

paper to the nature of a v chemical wood pulp.

. 2. The process of converting old paper containing ground wood into chemical wood. 

